/* $Header: /roq/tiff/tif_lzw.c 1     11/02/99 4:39p Zaphod $ */



/*

 * Copyright (c) 1988-1996 Sam Leffler

 * Copyright (c) 1991-1996 Silicon Graphics, Inc.

 *

 * Permission to use, copy, modify, distribute, and sell this software and 

 * its documentation for any purpose is hereby granted without fee, provided

 * that (i) the above copyright notices and this permission notice appear in

 * all copies of the software and related documentation, and (ii) the names of

 * Sam Leffler and Silicon Graphics may not be used in any advertising or

 * publicity relating to the software without the specific, prior written

 * permission of Sam Leffler and Silicon Graphics.

 * 

 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 

 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 

 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  

 * 

 * IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR

 * ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,

 * OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,

 * WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 

 * LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 

 * OF THIS SOFTWARE.

 */



#include "tiffiop.h"

#ifdef LZW_SUPPORT

/*

 * TIFF Library.

 * Rev 5.0 Lempel-Ziv & Welch Compression Support

 *

 * This code is derived from the compress program whose code is

 * derived from software contributed to Berkeley by James A. Woods,

 * derived from original work by Spencer Thomas and Joseph Orost.

 *

 * The original Berkeley copyright notice appears below in its entirety.

 */

#include "tif_predict.h"



#include <assert.h>

#include <stdio.h>



/*

 * NB: The 5.0 spec describes a different algorithm than Aldus

 *     implements.  Specifically, Aldus does code length transitions

 *     one code earlier than should be done (for real LZW).

 *     Earlier versions of this library implemented the correct

 *     LZW algorithm, but emitted codes in a bit order opposite

 *     to the TIFF spec.  Thus, to maintain compatibility w/ Aldus

 *     we interpret MSB-LSB ordered codes to be images written w/

 *     old versions of this library, but otherwise adhere to the

 *     Aldus "off by one" algorithm.

 *

 * Future revisions to the TIFF spec are expected to "clarify this issue".

 */

#define	LZW_COMPAT		/* include backwards compatibility code */

/*

 * Each strip of data is supposed to be terminated by a CODE_EOI.

 * If the following #define is included, the decoder will also

 * check for end-of-strip w/o seeing this code.  This makes the

 * library more robust, but also slower.

 */

#define	LZW_CHECKEOS		/* include checks for strips w/o EOI code */



#define MAXCODE(n)	((1L<<(n))-1)

/*

 * The TIFF spec specifies that encoded bit

 * strings range from 9 to 12 bits.

 */

#define	BITS_MIN	9		/* start with 9 bits */

#define	BITS_MAX	12		/* max of 12 bit strings */

/* predefined codes */

#define	CODE_CLEAR	256		/* code to clear string table */

#define	CODE_EOI	257		/* end-of-information code */

#define CODE_FIRST	258		/* first free code entry */

#define	CODE_MAX	MAXCODE(BITS_MAX)

#define	HSIZE		9001L		/* 91% occupancy */

#define	HSHIFT		(13-8)

#ifdef LZW_COMPAT

/* NB: +1024 is for compatibility with old files */

#define	CSIZE		(MAXCODE(BITS_MAX)+1024L)

#else

#define	CSIZE		(MAXCODE(BITS_MAX)+1L)

#endif



/*

 * State block for each open TIFF file using LZW

 * compression/decompression.  Note that the predictor

 * state block must be first in this data structure.

 */

typedef	struct {

	TIFFPredictorState predict;	/* predictor super class */



	u_short		nbits;		/* # of bits/code */

	u_short		maxcode;	/* maximum code for lzw_nbits */

	u_short		free_ent;	/* next free entry in hash table */

	long		nextdata;	/* next bits of i/o */

	long		nextbits;	/* # of valid bits in lzw_nextdata */

} LZWBaseState;



#define	lzw_nbits	base.nbits

#define	lzw_maxcode	base.maxcode

#define	lzw_free_ent	base.free_ent

#define	lzw_nextdata	base.nextdata

#define	lzw_nextbits	base.nextbits



/*

 * Decoding-specific state.

 */

typedef struct code_ent {

	struct code_ent *next;

	u_short	length;			/* string len, including this token */

	u_char	value;			/* data value */

	u_char	firstchar;		/* first token of string */

} code_t;



typedef	int (*decodeFunc)(TIFF*, tidata_t, tsize_t, tsample_t);



typedef struct {

	LZWBaseState base;

	long	dec_nbitsmask;		/* lzw_nbits 1 bits, right adjusted */

	long	dec_restart;		/* restart count */

#ifdef LZW_CHECKEOS

	long	dec_bitsleft;		/* available bits in raw data */

#endif

	decodeFunc dec_decode;		/* regular or backwards compatible */

	code_t*	dec_codep;		/* current recognized code */

	code_t*	dec_oldcodep;		/* previously recognized code */

	code_t*	dec_free_entp;		/* next free entry */

	code_t*	dec_maxcodep;		/* max available entry */

	code_t*	dec_codetab;		/* kept separate for small machines */

} LZWDecodeState;



/*

 * Encoding-specific state.

 */

typedef uint16 hcode_t;			/* codes fit in 16 bits */

typedef struct {

	long	hash;

	hcode_t	code;

} hash_t;



typedef struct {

	LZWBaseState base;

	int	enc_oldcode;		/* last code encountered */

	long	enc_checkpoint;		/* point at which to clear table */

#define CHECK_GAP	10000		/* enc_ratio check interval */

	long	enc_ratio;		/* current compression ratio */

	long	enc_incount;		/* (input) data bytes encoded */

	long	enc_outcount;		/* encoded (output) bytes */

	tidata_t enc_rawlimit;		/* bound on tif_rawdata buffer */

	hash_t*	enc_hashtab;		/* kept separate for small machines */

} LZWEncodeState;



#define	LZWState(tif)		((LZWBaseState*) (tif)->tif_data)

#define	DecoderState(tif)	((LZWDecodeState*) LZWState(tif))

#define	EncoderState(tif)	((LZWEncodeState*) LZWState(tif))



static	int LZWDecode(TIFF*, tidata_t, tsize_t, tsample_t);

#ifdef LZW_COMPAT

static	int LZWDecodeCompat(TIFF*, tidata_t, tsize_t, tsample_t);

#endif

static	void cl_hash(LZWEncodeState*);



/*

 * LZW Decoder.

 */



#ifdef LZW_CHECKEOS

/*

 * This check shouldn't be necessary because each

 * strip is suppose to be terminated with CODE_EOI.

 */

#define	NextCode(_tif, _sp, _bp, _code, _get) {				\
	if ((_sp)->dec_bitsleft < nbits) {				\
		TIFFWarning(_tif->tif_name,				\
		    "LZWDecode: Strip %d not terminated with EOI code", \
		    _tif->tif_curstrip);				\
		_code = CODE_EOI;					\
	} else {							\
		_get(_sp,_bp,_code);					\
		(_sp)->dec_bitsleft -= nbits;				\
	}								\
}

#else

#define	NextCode(tif, sp, bp, code, get) get(sp, bp, code)

#endif



static int

LZWSetupDecode(TIFF* tif)

{

	LZWDecodeState* sp = DecoderState(tif);

	static char module[] = " LZWSetupDecode";

	int code;



	assert(sp != NULL);

	if (sp->dec_codetab == NULL) {

		sp->dec_codetab = (code_t*)_TIFFmalloc(CSIZE*sizeof (code_t));

		if (sp->dec_codetab == NULL) {

			TIFFError(module, "No space for LZW code table");

			return (0);

		}

		/*

		 * Pre-load the table.

		 */

		for (code = 255; code >= 0; code--) {

			sp->dec_codetab[code].value = code;

			sp->dec_codetab[code].firstchar = code;

			sp->dec_codetab[code].length = 1;

			sp->dec_codetab[code].next = NULL;

		}

	}

	return (1);

}



/*

 * Setup state for decoding a strip.

 */

static int

LZWPreDecode(TIFF* tif, tsample_t s)

{

	LZWDecodeState *sp = DecoderState(tif);



	(void) s;

	assert(sp != NULL);

	/*

	 * Check for old bit-reversed codes.

	 */

	if (tif->tif_rawdata[0] == 0 && (tif->tif_rawdata[1] & 0x1)) {

#ifdef LZW_COMPAT

		if (!sp->dec_decode) {

			TIFFWarning(tif->tif_name,

			    "Old-style LZW codes, convert file");

			/*

			 * Override default decoding methods with

			 * ones that deal with the old coding.

			 * Otherwise the predictor versions set

			 * above will call the compatibility routines

			 * through the dec_decode method.

			 */

			tif->tif_decoderow = LZWDecodeCompat;

			tif->tif_decodestrip = LZWDecodeCompat;

			tif->tif_decodetile = LZWDecodeCompat;

			/*

			 * If doing horizontal differencing, must

			 * re-setup the predictor logic since we

			 * switched the basic decoder methods...

			 */

			(*tif->tif_setupdecode)(tif);

			sp->dec_decode = LZWDecodeCompat;

		}

		sp->lzw_maxcode = MAXCODE(BITS_MIN);

#else /* !LZW_COMPAT */

		if (!sp->dec_decode) {

			TIFFError(tif->tif_name,

			    "Old-style LZW codes not supported");

			sp->dec_decode = LZWDecode;

		}

		return (0);

#endif/* !LZW_COMPAT */

	} else {

		sp->lzw_maxcode = MAXCODE(BITS_MIN)-1;

		sp->dec_decode = LZWDecode;

	}

	sp->lzw_nbits = BITS_MIN;

	sp->lzw_nextbits = 0;

	sp->lzw_nextdata = 0;



	sp->dec_restart = 0;

	sp->dec_nbitsmask = MAXCODE(BITS_MIN);

#ifdef LZW_CHECKEOS

	sp->dec_bitsleft = tif->tif_rawcc << 3;

#endif

	sp->dec_free_entp = sp->dec_codetab + CODE_FIRST;

	/*

	 * Zero entries that are not yet filled in.  We do

	 * this to guard against bogus input data that causes

	 * us to index into undefined entries.  If you can

	 * come up with a way to safely bounds-check input codes

	 * while decoding then you can remove this operation.

	 */

	_TIFFmemset(sp->dec_free_entp, 0, (CSIZE-CODE_FIRST)*sizeof (code_t));

	sp->dec_oldcodep = &sp->dec_codetab[-1];

	sp->dec_maxcodep = &sp->dec_codetab[sp->dec_nbitsmask-1];

	return (1);

}



/*

 * Decode a "hunk of data".

 */

#define	GetNextCode(sp, bp, code) {				\
	nextdata = (nextdata<<8) | *(bp)++;			\
	nextbits += 8;						\
	if (nextbits < nbits) {					\
		nextdata = (nextdata<<8) | *(bp)++;		\
		nextbits += 8;					\
	}							\
	code = (hcode_t)((nextdata >> (nextbits-nbits)) & nbitsmask);	\
	nextbits -= nbits;					\
}



static void

codeLoop(TIFF* tif)

{

	TIFFError(tif->tif_name,

	    "LZWDecode: Bogus encoding, loop in the code table; scanline %d",

	    tif->tif_row);

}



static int

LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)

{

	LZWDecodeState *sp = DecoderState(tif);

	char *op = (char*) op0;

	long occ = (long) occ0;

	char *tp;

	u_char *bp;

	hcode_t code;

	int len;

	long nbits, nextbits, nextdata, nbitsmask;

	code_t *codep, *free_entp, *maxcodep, *oldcodep;



	(void) s;

	assert(sp != NULL);

	/*

	 * Restart interrupted output operation.

	 */

	if (sp->dec_restart) {

		long residue;



		codep = sp->dec_codep;

		residue = codep->length - sp->dec_restart;

		if (residue > occ) {

			/*

			 * Residue from previous decode is sufficient

			 * to satisfy decode request.  Skip to the

			 * start of the decoded string, place decoded

			 * values in the output buffer, and return.

			 */

			sp->dec_restart += occ;

			do {

				codep = codep->next;

			} while (--residue > occ && codep);

			if (codep) {

				tp = op + occ;

				do {

					*--tp = codep->value;

					codep = codep->next;

				} while (--occ && codep);

			}

			return (1);

		}

		/*

		 * Residue satisfies only part of the decode request.

		 */

		op += residue, occ -= residue;

		tp = op;

		do {

			int t;

			--tp;

			t = codep->value;

			codep = codep->next;

			*tp = t;

		} while (--residue && codep);

		sp->dec_restart = 0;

	}



	bp = (u_char *)tif->tif_rawcp;

	nbits = sp->lzw_nbits;

	nextdata = sp->lzw_nextdata;

	nextbits = sp->lzw_nextbits;

	nbitsmask = sp->dec_nbitsmask;

	oldcodep = sp->dec_oldcodep;

	free_entp = sp->dec_free_entp;

	maxcodep = sp->dec_maxcodep;



	while (occ > 0) {

		NextCode(tif, sp, bp, code, GetNextCode);

		if (code == CODE_EOI)

			break;

		if (code == CODE_CLEAR) {

			free_entp = sp->dec_codetab + CODE_FIRST;

			nbits = BITS_MIN;

			nbitsmask = MAXCODE(BITS_MIN);

			maxcodep = sp->dec_codetab + nbitsmask-1;

			NextCode(tif, sp, bp, code, GetNextCode);

			if (code == CODE_EOI)

				break;

			*op++ = code, occ--;

			oldcodep = sp->dec_codetab + code;

			continue;

		}

		codep = sp->dec_codetab + code;



		/*

	 	 * Add the new entry to the code table.

	 	 */

		assert(&sp->dec_codetab[0] <= free_entp && free_entp < &sp->dec_codetab[CSIZE]);

		free_entp->next = oldcodep;

		free_entp->firstchar = free_entp->next->firstchar;

		free_entp->length = free_entp->next->length+1;

		free_entp->value = (codep < free_entp) ?

		    codep->firstchar : free_entp->firstchar;

		if (++free_entp > maxcodep) {

			if (++nbits > BITS_MAX)		/* should not happen */

				nbits = BITS_MAX;

			nbitsmask = MAXCODE(nbits);

			maxcodep = sp->dec_codetab + nbitsmask-1;

		}

		oldcodep = codep;

		if (code >= 256) {

			/*

		 	 * Code maps to a string, copy string

			 * value to output (written in reverse).

		 	 */

			if (codep->length > occ) {

				/*

				 * String is too long for decode buffer,

				 * locate portion that will fit, copy to

				 * the decode buffer, and setup restart

				 * logic for the next decoding call.

				 */

				sp->dec_codep = codep;

				do {

					codep = codep->next;

				} while (codep && codep->length > occ);

				if (codep) {

					sp->dec_restart = occ;

					tp = op + occ;

					do  {

						*--tp = codep->value;

						codep = codep->next;

					}  while (--occ && codep);

					if (codep)

						codeLoop(tif);

				}

				break;

			}

			len = codep->length;

			tp = op + len;

			do {

				int t;

				--tp;

				t = codep->value;

				codep = codep->next;

				*tp = t;

			} while (codep && tp > op);

			if (codep) {

			    codeLoop(tif);

			    break;

			}

			op += len, occ -= len;

		} else

			*op++ = code, occ--;

	}



	tif->tif_rawcp = (tidata_t) bp;

	sp->lzw_nbits = (u_short) nbits;

	sp->lzw_nextdata = nextdata;

	sp->lzw_nextbits = nextbits;

	sp->dec_nbitsmask = nbitsmask;

	sp->dec_oldcodep = oldcodep;

	sp->dec_free_entp = free_entp;

	sp->dec_maxcodep = maxcodep;



	if (occ > 0) {

		TIFFError(tif->tif_name,

		"LZWDecode: Not enough data at scanline %d (short %d bytes)",

		    tif->tif_row, occ);

		return (0);

	}

	return (1);

}



#ifdef LZW_COMPAT

/*

 * Decode a "hunk of data" for old images.

 */

#define	GetNextCodeCompat(sp, bp, code) {			\
	nextdata |= (u_long) *(bp)++ << nextbits;		\
	nextbits += 8;						\
	if (nextbits < nbits) {					\
		nextdata |= (u_long) *(bp)++ << nextbits;	\
		nextbits += 8;					\
	}							\
	code = (hcode_t)(nextdata & nbitsmask);			\
	nextdata >>= nbits;					\
	nextbits -= nbits;					\
}



static int

LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)

{

	LZWDecodeState *sp = DecoderState(tif);

	char *op = (char*) op0;

	long occ = (long) occ0;

	char *tp;

	u_char *bp;

	int code, nbits;

	long nextbits, nextdata, nbitsmask;

	code_t *codep, *free_entp, *maxcodep, *oldcodep;



	(void) s;

	assert(sp != NULL);

	/*

	 * Restart interrupted output operation.

	 */

	if (sp->dec_restart) {

		long residue;



		codep = sp->dec_codep;

		residue = codep->length - sp->dec_restart;

		if (residue > occ) {

			/*

			 * Residue from previous decode is sufficient

			 * to satisfy decode request.  Skip to the

			 * start of the decoded string, place decoded

			 * values in the output buffer, and return.

			 */

			sp->dec_restart += occ;

			do {

				codep = codep->next;

			} while (--residue > occ);

			tp = op + occ;

			do {

				*--tp = codep->value;

				codep = codep->next;

			} while (--occ);

			return (1);

		}

		/*

		 * Residue satisfies only part of the decode request.

		 */

		op += residue, occ -= residue;

		tp = op;

		do {

			*--tp = codep->value;

			codep = codep->next;

		} while (--residue);

		sp->dec_restart = 0;

	}



	bp = (u_char *)tif->tif_rawcp;

	nbits = sp->lzw_nbits;

	nextdata = sp->lzw_nextdata;

	nextbits = sp->lzw_nextbits;

	nbitsmask = sp->dec_nbitsmask;

	oldcodep = sp->dec_oldcodep;

	free_entp = sp->dec_free_entp;

	maxcodep = sp->dec_maxcodep;



	while (occ > 0) {

		NextCode(tif, sp, bp, code, GetNextCodeCompat);

		if (code == CODE_EOI)

			break;

		if (code == CODE_CLEAR) {

			free_entp = sp->dec_codetab + CODE_FIRST;

			nbits = BITS_MIN;

			nbitsmask = MAXCODE(BITS_MIN);

			maxcodep = sp->dec_codetab + nbitsmask;

			NextCode(tif, sp, bp, code, GetNextCodeCompat);

			if (code == CODE_EOI)

				break;

			*op++ = code, occ--;

			oldcodep = sp->dec_codetab + code;

			continue;

		}

		codep = sp->dec_codetab + code;



		/*

	 	 * Add the new entry to the code table.

	 	 */

		assert(&sp->dec_codetab[0] <= free_entp && free_entp < &sp->dec_codetab[CSIZE]);

		free_entp->next = oldcodep;

		free_entp->firstchar = free_entp->next->firstchar;

		free_entp->length = free_entp->next->length+1;

		free_entp->value = (codep < free_entp) ?

		    codep->firstchar : free_entp->firstchar;

		if (++free_entp > maxcodep) {

			if (++nbits > BITS_MAX)		/* should not happen */

				nbits = BITS_MAX;

			nbitsmask = MAXCODE(nbits);

			maxcodep = sp->dec_codetab + nbitsmask;

		}

		oldcodep = codep;

		if (code >= 256) {

			/*

		 	 * Code maps to a string, copy string

			 * value to output (written in reverse).

		 	 */

			if (codep->length > occ) {

				/*

				 * String is too long for decode buffer,

				 * locate portion that will fit, copy to

				 * the decode buffer, and setup restart

				 * logic for the next decoding call.

				 */

				sp->dec_codep = codep;

				do {

					codep = codep->next;

				} while (codep->length > occ);

				sp->dec_restart = occ;

				tp = op + occ;

				do  {

					*--tp = codep->value;

					codep = codep->next;

				}  while (--occ);

				break;

			}

			op += codep->length, occ -= codep->length;

			tp = op;

			do {

				*--tp = codep->value;

			} while (codep = codep->next);

		} else

			*op++ = code, occ--;

	}



	tif->tif_rawcp = (tidata_t) bp;

	sp->lzw_nbits = nbits;

	sp->lzw_nextdata = nextdata;

	sp->lzw_nextbits = nextbits;

	sp->dec_nbitsmask = nbitsmask;

	sp->dec_oldcodep = oldcodep;

	sp->dec_free_entp = free_entp;

	sp->dec_maxcodep = maxcodep;



	if (occ > 0) {

		TIFFError(tif->tif_name,

	    "LZWDecodeCompat: Not enough data at scanline %d (short %d bytes)",

		    tif->tif_row, occ);

		return (0);

	}

	return (1);

}

#endif /* LZW_COMPAT */



/*

 * LZW Encoding.

 */



static int

LZWSetupEncode(TIFF* tif)

{

	LZWEncodeState* sp = EncoderState(tif);

	static char module[] = "LZWSetupEncode";



	assert(sp != NULL);

	sp->enc_hashtab = (hash_t*) _TIFFmalloc(HSIZE*sizeof (hash_t));

	if (sp->enc_hashtab == NULL) {

		TIFFError(module, "No space for LZW hash table");

		return (0);

	}

	return (1);

}



/*

 * Reset encoding state at the start of a strip.

 */

static int

LZWPreEncode(TIFF* tif, tsample_t s)

{

	LZWEncodeState *sp = EncoderState(tif);



	(void) s;

	assert(sp != NULL);

	sp->lzw_nbits = BITS_MIN;

	sp->lzw_maxcode = MAXCODE(BITS_MIN);

	sp->lzw_free_ent = CODE_FIRST;

	sp->lzw_nextbits = 0;

	sp->lzw_nextdata = 0;

	sp->enc_checkpoint = CHECK_GAP;

	sp->enc_ratio = 0;

	sp->enc_incount = 0;

	sp->enc_outcount = 0;

	/*

	 * The 4 here insures there is space for 2 max-sized

	 * codes in LZWEncode and LZWPostDecode.

	 */

	sp->enc_rawlimit = tif->tif_rawdata + tif->tif_rawdatasize-1 - 4;

	cl_hash(sp);		/* clear hash table */

	sp->enc_oldcode = (hcode_t) -1;	/* generates CODE_CLEAR in LZWEncode */

	return (1);

}



#define	CALCRATIO(sp, rat) {					\
	if (incount > 0x007fffff) { /* NB: shift will overflow */\
		rat = outcount >> 8;				\
		rat = (rat == 0 ? 0x7fffffff : incount/rat);	\
	} else							\
		rat = (incount<<8) / outcount;			\
}

#define	PutNextCode(op, c) {					\
	nextdata = (nextdata << nbits) | c;			\
	nextbits += nbits;					\
	*op++ = (u_char)(nextdata >> (nextbits-8));		\
	nextbits -= 8;						\
	if (nextbits >= 8) {					\
		*op++ = (u_char)(nextdata >> (nextbits-8));	\
		nextbits -= 8;					\
	}							\
	outcount += nbits;					\
}



/*

 * Encode a chunk of pixels.

 *

 * Uses an open addressing double hashing (no chaining) on the 

 * prefix code/next character combination.  We do a variant of

 * Knuth's algorithm D (vol. 3, sec. 6.4) along with G. Knott's

 * relatively-prime secondary probe.  Here, the modular division

 * first probe is gives way to a faster exclusive-or manipulation. 

 * Also do block compression with an adaptive reset, whereby the

 * code table is cleared when the compression ratio decreases,

 * but after the table fills.  The variable-length output codes

 * are re-sized at this point, and a CODE_CLEAR is generated

 * for the decoder. 

 */

static int

LZWEncode(TIFF* tif, tidata_t bp, tsize_t cc, tsample_t s)

{

	register LZWEncodeState *sp = EncoderState(tif);

	register long fcode;

	register hash_t *hp;

	register int h, c;

	hcode_t ent;

	long disp;

	long incount, outcount, checkpoint;

	long nextdata, nextbits;

	int free_ent, maxcode, nbits;

	tidata_t op, limit;



	(void) s;

	if (sp == NULL)

		return (0);

	/*

	 * Load local state.

	 */

	incount = sp->enc_incount;

	outcount = sp->enc_outcount;

	checkpoint = sp->enc_checkpoint;

	nextdata = sp->lzw_nextdata;

	nextbits = sp->lzw_nextbits;

	free_ent = sp->lzw_free_ent;

	maxcode = sp->lzw_maxcode;

	nbits = sp->lzw_nbits;

	op = tif->tif_rawcp;

	limit = sp->enc_rawlimit;

	ent = sp->enc_oldcode;



	if (ent == (hcode_t) -1 && cc > 0) {

		/*

		 * NB: This is safe because it can only happen

		 *     at the start of a strip where we know there

		 *     is space in the data buffer.

		 */

		PutNextCode(op, CODE_CLEAR);

		ent = *bp++; cc--; incount++;

	}

	while (cc > 0) {

		c = *bp++; cc--; incount++;

		fcode = ((long)c << BITS_MAX) + ent;

		h = (c << HSHIFT) ^ ent;	/* xor hashing */

#ifdef _WINDOWS

		/*

		 * Check hash index for an overflow.

		 */

		if (h >= HSIZE)

			h -= HSIZE;

#endif

		hp = &sp->enc_hashtab[h];

		if (hp->hash == fcode) {

			ent = hp->code;

			continue;

		}

		if (hp->hash >= 0) {

			/*

			 * Primary hash failed, check secondary hash.

			 */

			disp = HSIZE - h;

			if (h == 0)

				disp = 1;

			do {

#ifndef _WINDOWS

				if ((hp -= disp) < sp->enc_hashtab)

					hp += HSIZE;

#else

				/*

				 * Avoid pointer arithmetic 'cuz of

				 * wraparound problems with segments.

				 */

				if ((h -= disp) < 0)

					h += HSIZE;

				hp = &sp->enc_hashtab[h];

#endif

				if (hp->hash == fcode) {

					ent = hp->code;

					goto hit;

				}

			} while (hp->hash >= 0);

		}

		/*

		 * New entry, emit code and add to table.

		 */

		/*

		 * Verify there is space in the buffer for the code

		 * and any potential Clear code that might be emitted

		 * below.  The value of limit is setup so that there

		 * are at least 4 bytes free--room for 2 codes.

		 */

		if (op > limit) {

			tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);

			TIFFFlushData1(tif);

			op = tif->tif_rawdata;

		}

		PutNextCode(op, ent);

		ent = c;

		hp->code = free_ent++;

		hp->hash = fcode;

		if (free_ent == CODE_MAX-1) {

			/* table is full, emit clear code and reset */

			cl_hash(sp);

			sp->enc_ratio = 0;

			incount = 0;

			outcount = 0;

			free_ent = CODE_FIRST;

			PutNextCode(op, CODE_CLEAR);

			nbits = BITS_MIN;

			maxcode = MAXCODE(BITS_MIN);

		} else {

			/*

			 * If the next entry is going to be too big for

			 * the code size, then increase it, if possible.

			 */

			if (free_ent > maxcode) {

				nbits++;

				assert(nbits <= BITS_MAX);

				maxcode = (int) MAXCODE(nbits);

			} else if (incount >= checkpoint) {

				long rat;

				/*

				 * Check compression ratio and, if things seem

				 * to be slipping, clear the hash table and

				 * reset state.  The compression ratio is a

				 * 24+8-bit fractional number.

				 */

				checkpoint = incount+CHECK_GAP;

				CALCRATIO(sp, rat);

				if (rat <= sp->enc_ratio) {

					cl_hash(sp);

					sp->enc_ratio = 0;

					incount = 0;

					outcount = 0;

					free_ent = CODE_FIRST;

					PutNextCode(op, CODE_CLEAR);

					nbits = BITS_MIN;

					maxcode = MAXCODE(BITS_MIN);

				} else

					sp->enc_ratio = rat;

			}

		}

	hit:

		;

	}



	/*

	 * Restore global state.

	 */

	sp->enc_incount = incount;

	sp->enc_outcount = outcount;

	sp->enc_checkpoint = checkpoint;

	sp->enc_oldcode = ent;

	sp->lzw_nextdata = nextdata;

	sp->lzw_nextbits = nextbits;

	sp->lzw_free_ent = free_ent;

	sp->lzw_maxcode = maxcode;

	sp->lzw_nbits = nbits;

	tif->tif_rawcp = op;

	return (1);

}



/*

 * Finish off an encoded strip by flushing the last

 * string and tacking on an End Of Information code.

 */

static int

LZWPostEncode(TIFF* tif)

{

	register LZWEncodeState *sp = EncoderState(tif);

	tidata_t op = tif->tif_rawcp;

	long nextbits = sp->lzw_nextbits;

	long nextdata = sp->lzw_nextdata;

	long outcount = sp->enc_outcount;

	int nbits = sp->lzw_nbits;



	if (op > sp->enc_rawlimit) {

		tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);

		TIFFFlushData1(tif);

		op = tif->tif_rawdata;

	}

	if (sp->enc_oldcode != (hcode_t) -1) {

		PutNextCode(op, sp->enc_oldcode);

		sp->enc_oldcode = (hcode_t) -1;

	}

	PutNextCode(op, CODE_EOI);

	if (nextbits > 0) 

		*op++ = (u_char)(nextdata << (8-nextbits));

	tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);

	return (1);

}



/*

 * Reset encoding hash table.

 */

static void

cl_hash(LZWEncodeState* sp)

{

	register hash_t *hp = &sp->enc_hashtab[HSIZE-1];

	register long i = HSIZE-8;



 	do {

		i -= 8;

		hp[-7].hash = -1;

		hp[-6].hash = -1;

		hp[-5].hash = -1;

		hp[-4].hash = -1;

		hp[-3].hash = -1;

		hp[-2].hash = -1;

		hp[-1].hash = -1;

		hp[ 0].hash = -1;

		hp -= 8;

	} while (i >= 0);

    	for (i += 8; i > 0; i--, hp--)

		hp->hash = -1;

}



static void

LZWCleanup(TIFF* tif)

{

	if (tif->tif_data) {

		if (tif->tif_mode == O_RDONLY) {

			if (DecoderState(tif)->dec_codetab)

				_TIFFfree(DecoderState(tif)->dec_codetab);

		} else {

			if (EncoderState(tif)->enc_hashtab)

				_TIFFfree(EncoderState(tif)->enc_hashtab);

		}

		_TIFFfree(tif->tif_data);

		tif->tif_data = NULL;

	}

}



int

TIFFInitLZW(TIFF* tif, int scheme)

{

	assert(scheme == COMPRESSION_LZW);

	/*

	 * Allocate state block so tag methods have storage to record values.

	 */

	if (tif->tif_mode == O_RDONLY) {

		tif->tif_data = (tidata_t) _TIFFmalloc(sizeof (LZWDecodeState));

		if (tif->tif_data == NULL)

			goto bad;

		DecoderState(tif)->dec_codetab = NULL;

		DecoderState(tif)->dec_decode = NULL;

	} else {

		tif->tif_data = (tidata_t) _TIFFmalloc(sizeof (LZWEncodeState));

		if (tif->tif_data == NULL)

			goto bad;

		EncoderState(tif)->enc_hashtab = NULL;

	}

	/*

	 * Install codec methods.

	 */

	tif->tif_setupdecode = LZWSetupDecode;

	tif->tif_predecode = LZWPreDecode;

	tif->tif_decoderow = LZWDecode;

	tif->tif_decodestrip = LZWDecode;

	tif->tif_decodetile = LZWDecode;

	tif->tif_setupencode = LZWSetupEncode;

	tif->tif_preencode = LZWPreEncode;

	tif->tif_postencode = LZWPostEncode;

	tif->tif_encoderow = LZWEncode;

	tif->tif_encodestrip = LZWEncode;

	tif->tif_encodetile = LZWEncode;

	tif->tif_cleanup = LZWCleanup;

	/*

	 * Setup predictor setup.

	 */

	(void) TIFFPredictorInit(tif);

	return (1);

bad:

	TIFFError("TIFFInitLZW", "No space for LZW state block");

	return (0);

}



/*

 * Copyright (c) 1985, 1986 The Regents of the University of California.

 * All rights reserved.

 *

 * This code is derived from software contributed to Berkeley by

 * James A. Woods, derived from original work by Spencer Thomas

 * and Joseph Orost.

 *

 * Redistribution and use in source and binary forms are permitted

 * provided that the above copyright notice and this paragraph are

 * duplicated in all such forms and that any documentation,

 * advertising materials, and other materials related to such

 * distribution and use acknowledge that the software was developed

 * by the University of California, Berkeley.  The name of the

 * University may not be used to endorse or promote products derived

 * from this software without specific prior written permission.

 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR

 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED

 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

 */

#endif /* LZW_SUPPORT */

